Compounded Semaglutide vs Brand (Ozempic & Wegovy): What's the Difference?

"Compounded semaglutide" and brand-name Ozempic or Wegovy all share the same active molecule, semaglutide. What changes is who makes the product, how it is formulated, how it is regulated, what it costs, and how the dose reaches the syringe. Those differences are the reason a number printed on a brand pen does not map cleanly onto a vial from a compounding source.

This is a neutral, third-person comparison written as reference information. Semaglutide in research-vial form is not approved for self-directed human use, and nothing here is dosing guidance or a claim about results. Any protocol decision belongs with a licensed clinician. For the unit math discussed later, the semaglutide calculator handles the conversions, and the full disclaimer applies to every figure below.

Same molecule, different products

Ozempic and Wegovy are both brand products from the same manufacturer, built on identical semaglutide chemistry. The brand split is about labeling, not a different drug.

• Ozempic: the brand labeled around blood sugar, sold in prefilled multi-dose pens with fixed click doses.
• Wegovy: the brand labeled around weight management, also a prefilled pen, with a titration schedule running up to 2.4 mg weekly.
• Compounded semaglutide: prepared by a pharmacy or supplier, usually shipped as a powder vial or a pre-mixed vial drawn with a separate insulin syringe.

The active ingredient can be the same across all three. The packaging, oversight, and the way a dose is measured are where they part ways.

Salt forms: the part most people miss

Brand Ozempic and Wegovy use the semaglutide base, the form studied in the trials those brands are built on. Some compounded and research vials are labeled instead as a salt: semaglutide sodium or semaglutide acetate. The salt is added during manufacturing, and it changes how a milligram on the label lines up with the base molecule.

• Base semaglutide: the form used in brand pens and in the published trial dosing figures.
• Semaglutide sodium or acetate: a salt form sometimes seen on compounded or research labels, where part of the labeled weight is the salt, not the active base.

FDA status: approved drug vs compounded preparation

This is the regulatory dividing line, and it is the clearest difference of the four.

• Ozempic and Wegovy are FDA-approved drugs. Each batch is made and tested under the approval, with set strength, purity, and labeling.
• Compounded semaglutide is not an FDA-approved product. Compounded preparations are not reviewed for safety, effectiveness, or quality the way an approved drug is, and content can vary by source.
• Research vials sold for laboratory use sit outside the human-drug framework entirely and are not intended for self-directed use.

Compounding expanded while brand pens were in shortage. As supply normalizes, the rules around what may be compounded shift, which is one reason availability and labeling on compounded sources change over time.

Cost and format

Price and packaging usually track together. Brand pens are pre-dosed and priced as finished approved products. Compounded vials are typically cheaper per milligram but shift the measuring work onto the user.

• Brand pens: dial or click to a fixed dose, no mixing, no math, priced at the higher end.
• Compounded vials: lower headline cost, but you reconstitute (if powder), calculate concentration, and draw each dose by hand on an insulin syringe.

The format difference is exactly why the dosing step is not the same between them.

Why dosing differs: pen clicks vs syringe units

A brand pen hides the concentration. You select 0.25 mg or 0.5 mg and the device delivers it. A vial does not, so the same milligram target becomes a different number of syringe units depending on how much water was added.

Worked example with a 5 mg powder vial:

1. Add 1 mL of bacteriostatic water to a 5 mg vial. Concentration is 5 mg / 1 mL = 5 mg/mL.
2. For a 0.25 mg target: 0.25 / 5 = 0.05 mL = 5 units on a U-100 insulin syringe.
3. For a 0.5 mg target from the same vial: 0.5 / 5 = 0.1 mL = 10 units.
4. Add 2 mL of water instead and the concentration halves to 2.5 mg/mL, so 0.25 mg now becomes 10 units, not 5.

Same target, different units, purely because the concentration changed. That is the trap when copying a brand pen dose onto a vial. Run the numbers with the semaglutide calculator, set the water volume with the reconstitution calculator, or convert a milligram figure to syringe units with the mg to units calculator. For the mixing step itself, see how to reconstitute semaglutide, and semaglutide units per dose for common targets.

Quick reference summary

• Molecule: all three use semaglutide; brand pens use the base form.
• Salt forms: compounded labels may read sodium or acetate, so mg may not match brand mg.
• FDA status: Ozempic and Wegovy are approved; compounded semaglutide is not reviewed the same way.
• Cost and format: pens are pre-dosed and pricier; vials are cheaper but need mixing and math.
• Dosing: pens click to a fixed dose; vials depend on concentration, so units change with water volume.

For deeper context on the molecule itself, see semaglutide vs tirzepatide, and to keep vial concentration, doses, and schedules logged in one place, the Stackr app tracks them. Always read the disclaimer before using any number here.